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Vulnerability Note VU#938323
Postfix local privilege escalation
OverviewThe Postfix MTA contains a local privilege escalation vulnerability.
I. DescriptionPostfix is an mail transport agent (MTA) that is used by several Unix-like operating systems. Symbolic links and hard links are types of files that reference other files. Unlike hard links, symbolic links can point to directories and use relative pathnames.
On some non-POSIX.1-2001 and X/Open XPG4v2 compliant systems, users can hardlink symlinks which are owned by the root user. Postfix allows root-owned symlinks to be used as a mail destination folder. A hard link to a Postfix root-owned symlink could point to a file that can be overwritten by Postfix, regardless of the permissions of the destination file.
II. ImpactA local, authenticated attacker may be able to overwrite arbitrary files, possibly gaining elevated privileges.
III. SolutionUpgrade
See http://article.gmane.org/gmane.mail.postfix.announce/110 for information about obtaining updated software. Users who do not compile Postfix from source should see the systems affected section below for a partial list of affected vendors.
Set mailbox permissions
Making the system mail spool directory root-owned may mitigate this vulnerability. See http://article.gmane.org/gmane.mail.postfix.announce/110 for specific information about this and other workarounds.
Systems Affected
| Vendor | Status | Date Updated |
|---|
| Apple Computer, Inc. | Unknown | 19-Aug-2008 |
| Conectiva Inc. | Unknown | 1-Aug-2008 |
| Cray Inc. | Unknown | 1-Aug-2008 |
| Debian GNU/Linux | Unknown | 1-Aug-2008 |
| DragonFly BSD Project | Not Vulnerable | 2-Aug-2008 |
| EMC Corporation | Unknown | 1-Aug-2008 |
| Engarde Secure Linux | Unknown | 1-Aug-2008 |
| F5 Networks, Inc. | Unknown | 1-Aug-2008 |
| Fedora Project | Unknown | 1-Aug-2008 |
| FreeBSD, Inc. | Unknown | 1-Aug-2008 |
| Fujitsu | Unknown | 1-Aug-2008 |
| Gentoo Linux | Vulnerable | 18-Aug-2008 |
| Hewlett-Packard Company | Unknown | 1-Aug-2008 |
| Hitachi | Unknown | 1-Aug-2008 |
| IBM Corporation | Unknown | 1-Aug-2008 |
| IBM Corporation (zseries) | Unknown | 1-Aug-2008 |
| IBM eServer | Unknown | 1-Aug-2008 |
| Ingrian Networks, Inc. | Unknown | 1-Aug-2008 |
| Juniper Networks, Inc. | Unknown | 1-Aug-2008 |
| Mandriva, Inc. | Vulnerable | 18-Aug-2008 |
| Microsoft Corporation | Unknown | 1-Aug-2008 |
| MontaVista Software, Inc. | Unknown | 1-Aug-2008 |
| NEC Corporation | Unknown | 1-Aug-2008 |
| NetBSD | Unknown | 1-Aug-2008 |
| Nokia | Unknown | 1-Aug-2008 |
| Novell, Inc. | Unknown | 1-Aug-2008 |
| Openwall GNU/*/Linux | Unknown | 1-Aug-2008 |
| QNX, Software Systems, Inc. | Unknown | 1-Aug-2008 |
| Red Hat, Inc. | Unknown | 1-Aug-2008 |
| Silicon Graphics, Inc. | Unknown | 1-Aug-2008 |
| Slackware Linux Inc. | Unknown | 1-Aug-2008 |
| Sony Corporation | Unknown | 1-Aug-2008 |
| Sun Microsystems, Inc. | Not Vulnerable | 19-Aug-2008 |
| SUSE Linux | Vulnerable | 18-Aug-2008 |
| The SCO Group | Unknown | 1-Aug-2008 |
| Turbolinux | Unknown | 1-Aug-2008 |
| Ubuntu | Vulnerable | 19-Aug-2008 |
| Unisys | Unknown | 1-Aug-2008 |
| Wind River Systems, Inc. | Unknown | 1-Aug-2008 |
References
ftp://ftp.porcupine.org/mirrors/postfix-release/index/html
http://article.gmane.org/gmane.mail.postfix.announce/110
http://linuxgazette.net/105/pitcher.html
http://en.wikipedia.org/wiki/Hard_links
http://en.wikipedia.org/wiki/Symbolic_link
Credit
Thanks to Wietse Venema for information that was used in this report. Sebastian Krahmer of SuSE is credited for discovering and reporting this issue.
This document was written by Ryan Giobbi.
Other Information
| Date Public | 08/18/2008 |
| Date First Published | 08/18/2008 03:52:50 PM |
| Date Last Updated | 08/19/2008 |
| CERT Advisory | |
| CVE Name | CVE-2008-2936 |
| Metric | 4.20 |
| Document Revision | 20 |
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